This invention relates to a process for forming a lanthanum aluminum compound which can be used in a silicon nitride composition that can be consolidated to form silicon nitride bodies of high density.
In general, silicon nitride by itself has limited usage. In order to produce materials for turbines, cutting tools, wear parts and the like, composites are needed which can be cold pressed and sintered to near theoretical density, that is, greater than about 96% of the theoretical density. U.S. Pat. Nos. 3,950,464 and 3,953,221 cite compositions of silicon nitride and sintering aids such as yttrium oxide and aluminum oxide to aid in densification. However, with the use of yttrium oxide alone, the material cannot be cold pressed and sintered to near theoretical density.
The process of this invention involves the reaction of mixtures of oxides of lanthanum and aluminum to form a lanthanum aluminum compound which when used in a silicon nitride composition results in a body of high density on consolidation.